There are about 50 cities across the globe in which at least one billionaire makes his or her home. The fact is, billionaires are a pretty rare breed. Having that much money is a rare thing. If it wasn't, one in every seven people – over a billion in total – would not be living in extreme poverty with less than $1.25 a day in earnings. Yet, this sad fact of world poverty aside, there are thousands of people, who through inheritance or innovation and ambition, have amassed a fortune that cannot be spent in their lifetime. These individuals are the 1% of the top 1% in the world. Billionaires make up 0.00000032% of the world's population. Together, these 1.645 people have a total net worth around $6.4 trillion. The billionaires of the world are not spread out equally. They are quite concentrated in a handful of cities around the world. These are the 25 cities with the most billionaires: